The development length of bars can be provided in the form of straight bar if available otherwise it may be partially straight and partially hooked. The anchorage is normally provided in the form of bends and hooks.
Anchoring Bars in Tension
- Hooks are provided normally in plain bars in tension.
- Deformed bars may be used without end anchorage if the development length requirement is satisfied.
- The hooks should always confirm to the specifications.
- The anchorage value of a bend shall be taken as 4 times the diameter of the bar for each 45° bend subject to a maximum of 16 times the diameter of bar.
- The anchorage value of a standard U type hook is equal 16 times the diameter of bar.
- The anchorage value of a standard 90° bend is 8 times the diameter.
Anchoring Bars in Compression
The anchorage length of bar in compression is equal to the development length of bars in compression. The compression bars require no special anchorage arrangements.
Anchoring Shear Reinforcement
(a) Stirrups: As per IS456, the development and anchorage length deemed to have provided in the stirrups when
- The stirrup bar is bent through an angle of atleast 90° around a bar of atleast its own diameter and is continued beyond the curve for a length of atleast eight times the bar diameter. (or) When the bar is bent through an angle of 135° and is continued beyond the curve for a length of at least six times the bar diameter.
- When the bar is bent through an angle of 180° and is continued beyond the curve for a length of atleast four times the bar diameter.
(b) Bent Up Bars: The development length of such bars is according to the development length of bars in tension allowing for hooks and bends if provided and measured as following
- In tension zone -from the end of sloping or inclined portion of bars.
- In compression zone from the mid depth of beam.